The incidence of coronary artery disease in women over age 55 equals that of men, but mortality is higher. Relative to the number of studies of exercise and coronary disease in men, the role of exercise in women has been overlooked. This project will seek to define the role of habitual exercise in reducing the risk of coronary artery disease in women. These objectives will be realized by correlating levels of exercise with coronary disease and likely mediators of risk, such as distribution and concentration of lipoprotein species and sex hormones. These objectives will be accomplished by studying a group of women with a wide range of exercise fitness -- varying from sedentary individuals to triathletes, recruited from the ethnically diverse population of the San Francisco Bay area. Exercise fitness levels will be quantitated by maximal oxygen uptake (MVO2). Daily physical activities and exercise history as well as pack- year smoking history and percent ideal body weight will be determined by means of an exercise and health questionnaire and correlated to measured fitness levels(MVO2). The presence of critical coronary stenosis will be established by non- invasive testing: ultrafast computed tomography of the coronary tree and treadmill exercise echocardiography. Women who have evidence of coronary artery disease by either of these tests will have a transesophageal echocardiogram with coronary vasodilatation to quantitate proximal coronary stenosis and measure coronary vascular flow reserve. An additional aim of this project will be to correlate results of these non- invasive tests with quantitative angiographic and intravascular ultrasound characterization of coronary lesions. This project is designed to help reduce the high morbidity and mortality of cardiovascular disease in post-menopausal women by defining an optimal level of regular habitual exercise that offers cardiovascular protection. This level will be expressed in terms of everyday activities or moderate intensity exercise so that it is wide applicable.